Adverse Events Are Common With Medical Cannabis for Chronic Pain, but Serious Harms Are Rare

Overall adverse event prevalence was 26.0% (95% CI: 13.2-41.2%). Psychiatric adverse events were most common (13.5%). Serious adverse events, cognitive adverse events, accidents, injuries, and dependence/withdrawal each occurred in fewer than 5% of patients. Longer follow-up (24+ weeks) was associated with more reported adverse events than shorter studies.

Systematic review and meta-analysis searching MEDLINE, EMBASE, PsycINFO, and CENTRAL. Included 39 non-randomized studies of adults or children with chronic pain using medical cannabis with at least 4 weeks of follow-up. GRADE approach used to assess certainty. Parallel guideline panel informed design.

Chronic pain patients and their clinicians need realistic information about medical cannabis side effects to make informed treatment decisions. This review provides the most comprehensive picture of what to expect: side effects are common but usually not serious.

Medical cannabis is increasingly prescribed for chronic pain, often as an alternative to opioids. Knowing that serious harms are uncommon can help contextualize the risk-benefit calculation, though the finding that adverse events increase with longer use warrants monitoring.

All evidence rated as very low certainty due to study design limitations. Non-randomized studies are prone to confounding and selection bias. Insufficient evidence comparing medical cannabis harms to alternatives like opioids. Adverse event definitions varied across studies.